JPS60219925A - Charging circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a charging circuit that is incorporated into a small electric device.

[Background Technique 2Ii3] Generally, the time required for one use of a rechargeable product using a secondary battery such as a NiCd battery is about 2 to 3 minutes, but the rated charging time is the shortest. Normally, it takes a very long time, such as one hour, for a single device, and if you try to charge it in a short time, you will need sufficient current capacity and heat capacity, which will increase the size of the charging circuit and overcharge prevention circuit. In addition, there was a problem of ν1 caused by gas generation inside the battery or a decrease in battery life.

[Object of the Invention] In view of the above-mentioned problems, the present invention provides high-current charging for a certain period of time at the initial stage of charging, so that it can be charged for one or several uses in a short time in an emergency. In addition to automatically switching to low-current charging after the This allows charging to be performed in a short time without sacrificing performance.

1 Disclosure of the Invention 1 The present invention provides a first average charging current that charges energy equivalent to N times of use of an electrical device (N is a number of 1 or more) in a relatively short time, and a first average charging current that charges energy equivalent to N times of use of an electrical device (N is a number of 1 or more), and at least 80% of the rated charging capacity of the battery. % or more over a relatively long period of time, and a second average charging current that takes a relatively long time to charge. In the side circuit, a switching transistor,
By inserting a temperature sensing element near the inverter components such as a transformer, the charging current is reduced as the temperature rises, without increasing the capacity of switching transistors or transformers. ,
This allows for emergency charging to be performed as quickly as permissible.

The figure shows an embodiment of the charging circuit of the present invention. 1
is a power supply circuit, in which AC input from a commercial power supply S passes through a protective resistor R1, is rectified and smoothed by a full-wave rectifier Ref and a capacitor C1, and supplies a DC voltage Vin to each circuit. The switching circuit 2 and the base circuit 3 constitute an input/output circuit, and the collector of the switching transistor Qsu+ has a primary winding of a transformer.
A secondary winding L2 is connected to the base via a base resistor Rb3 and a DC blocking capacitor cb, and a secondary winding L2 is connected to the emitter via an emitter resistor Re1.
75' are inserted in series. When the current fJ V s is turned on, the base current Ib is supplied to the transistor QSI11 through the starting resistor Rh and Rb2, and the collector current Ic begins to flow. Primary winding L1 of transformer
and the secondary winding L2 are connected so that positive feedback is applied, so the collector current rises rapidly and the transistor QSII
+ is switched on quickly. At this time, in the output circuit 4, the secondary voltage induced in the output winding passes through the diode D o + and the battery B to the choke filter L.
Although it is applied to both ends of O, almost no secondary current flows because the rate of change of voltage is high and the actance of the choke coil is large, so the collector current on the primary side can increase linearly. . A certain value of collector current (Ic
>hFEXIb), the base current and I+
Due to the lack of F E, the transistor Qsu+ cannot maintain the on state, so the collector-emitter voltage increases and the voltage applied to the winding L1 begins to decrease, which causes the base current to decrease through the winding L2. Therefore, this tendency is promoted by positive feedback, and the transistor Qs- is quickly cut off. When the transistor Qsw is cut off, the energy stored in the choke fill Lo when it was on is transferred to the output winding.

and discharged through the diode DO□, supplying charging current to battery B. Thereafter, similar operations are repeated at regular intervals.

Next, the overcurrent prevention circuit 5 will be explained. Voltage Vin
is further smoothed and stabilized by resistor Ric2, capacitor Cic2, and Zener diode Dz2, and this Zener voltage is divided by resistors R1 and R2 and applied to the base of transistor Q as reference voltage Vref. While the voltage vb of battery B is smaller than the sum of the reference voltage Vref and the base-emitter-lid voltage Vbe of transistor Q1, and Vb<Vref+Vbe, Ql is on and Q2 is off (so the base circuit 3 remains unchanged and the transistor QS- continues to oscillate, but charging progresses and the battery voltage C3Vb>V
When the voltage rises to ref+Vbe, the transistor Q2 turns on and draws the base current of the transistor Qs-, thereby stopping the oscillation of the transistor QSIll, thereby terminating the charging.

Next, a charging current switching circuit composed of a timer circuit 6 and a switching circuit 7 will be explained. The power supply voltage supplied to the timer IC is determined by step-down resistor Ric1 and smoothing capacitor Cic+.
and stabilized by Zener diode Dz1 and Vc
added to the c terminal. The timer circuit is reset by the rise of the Vcc voltage, and the time until a time-up signal is output to the output terminal Vout is set by an external resistor Rt and an external capacitor Ct. Switching circuit 7
consists of a transistor Qo and a resistor Re2, which are connected in parallel between the emitter ground of the switching transistor QsIll, and when the timer output is at "H" level, the transistor Qo is in the on state, so the emitter ground of the switching transistor Qsw is connected in parallel between the emitter ground of the switching transistor QsIll. The resistance value between is approximately the first emitter resistance Re and the second emitter resistance Re.
It is a parallel resistance with 2, and a large flfter current 1c
However, when the timer output changes to "L", the switching circuit 7 is turned off and the emitter resistance of the switching transistor Qsw becomes Rel. Since the flefter current Ic is limited, the output current 1o can also be switched to a small current for long-term charging.A capacitor Cs and a resistor Rs are connected across the primary winding of the transformer.
A spike absorption circuit 8 consisting of the following is connected.

In this embodiment, as a temperature sensing element, a POSISTOR Rp is inserted in series with the power supply line that supplies DC power supply voltage to the inverter, and this POSISTOR detects abnormal temperatures of inverter components such as switching transistors, transformers, choke fills, etc. By detecting the rise and limiting the input current to the inverter, damage to each electronic component is prevented.

For example, by connecting an SCR controlled by a temperature sensing element between the output terminal Vout of the timer circuit 6 and the ground, if the temperature sensing element detects an abnormal temperature, the short charging mode is immediately switched to the long charging mode. Switch to time charging mode,
The charging mode can be maintained for a long time even after the temperature drops again. In this way, it is possible to prevent the risk of a large current flowing again before the cause of the abnormality is removed.

[Effects of the Invention] As described above, the charging circuit of the present invention includes an inverter such as a switching transistor or a transformer in the primary side circuit of an inverter that converts a commercial power supply voltage into a charging voltage in a charging circuit equipped with a charging current switching circuit. By inserting a temperature sensing element placed near the component parts, the charging current decreases as the temperature rises. It has the advantage of being able to charge for emergency use in a short time without increasing the current capacity, and if the charging mode is switched using a temperature-sensitive element, the most efficient charging mode can be selected depending on the ambient conditions such as temperature. It has the advantage of being able to charge well.

[Brief explanation of drawings]

The figure is a circuit diagram showing an embodiment of the charging circuit of the present invention. 1 is a power supply circuit, 2 is a switching circuit, 3 is a base circuit, 4 is an output circuit, 5 is an overcharge prevention circuit, 6 is a timer circuit, 7 is a switching circuit, 8 is a spike absorption circuit, 9 is a charged battery, QsIll is a switching transistor, Ll is a primary winding, L2 is a feedback winding, L3 is an output winding,
Lo is a choke fill, Cb is a DC blocking capacitor, R
b, and RIJ2 are starting resistances, Rb is base resistance,
Re is an emitter resistance, Re 2 is a second emitter resistance, Do+ and Doo are diodes, QO is a transistor, B is a battery, and R11 is a temperature sensing element or posistor. Agent Patent Attorney Ishi 1) Choshichi

Claims (2)

[Claims] (1) A first average charging current that charges the energy equivalent to N uses of the electrical device (N is a number of 1 or more) in a relatively short time, and a comparatively In a charging circuit equipped with a charging current switching circuit that sequentially supplies a second average charging current that takes a long time to charge, a circuit on the primary side of an inverter that converts a commercial power supply voltage to a charging type). , a switching transistor,
A charging circuit characterized in that a temperature sensing element placed near an inverter component such as a transformer is inserted so that charging current decreases as the temperature rises. (2) Claims characterized in that the device is configured to switch from a short-time charging mode to a long-term charging mode using the temperature sensing element, and to maintain the long-term charging mode even if the temperature drops again. The charging circuit described in item 1.